This has been on before and is worth studying, and should be one of the first things explained . The use of the back foot in a foreward walk in Foxtrot mode. The lecturer had us take our shoes off and got us to use the whole of the back foot all the way to the tip of the toe. Then he had us doing it wrong, and that was coming of a flat foot. He then asked what was the front foot doing. The answer was it's bent at the knee. It will eventually bend at the knee but first it must be straight and only flex when the weight arrives. The casuall use of the rear foot is like building your house on sand, it doesn't matter what you do from then on its not going to be right. And then before you know where you are you've done it again.